+CC Conall On 3/9/24 14:06, Jonathan Cameron wrote: > On Tue, 5 Mar 2024 12:30:53 -0500 > Sean Anderson <sean.anderson@xxxxxxxxx> wrote: > >> Hi, >> >> When enabling UBSAN on a ZynqMP Ultrascale+, I see the following error during boot: >> >> [ 1.447628] ================================================================================ >> [ 1.447832] UBSAN: shift-out-of-bounds in ../drivers/iio/adc/xilinx-ams.c:426:16 >> [ 1.448019] shift exponent 66 is too large for 64-bit type 'long long unsigned int' >> [ 1.448211] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.6.20+ #90 >> [ 1.448368] Hardware name: xlnx,zynqmp (DT) >> [ 1.448475] Call trace: >> [ 1.448547] dump_backtrace+0x9c/0x11c >> [ 1.448655] show_stack+0x18/0x24 >> [ 1.448749] dump_stack_lvl+0xac/0xd4 >> [ 1.448853] dump_stack+0x18/0x24 >> [ 1.448947] ubsan_epilogue+0x10/0x44 >> [ 1.449051] __ubsan_handle_shift_out_of_bounds+0x98/0x134 >> [ 1.449191] ams_enable_channel_sequence+0x22c/0x23c >> [ 1.449324] ams_probe+0x570/0x6d4 >> [ 1.449423] platform_probe+0x68/0x108 >> [ 1.449530] really_probe+0x158/0x3b0 >> [ 1.449632] __driver_probe_device+0x88/0x1a0 >> [ 1.449747] driver_probe_device+0x3c/0x138 >> [ 1.449859] __driver_attach+0xe4/0x1bc >> [ 1.449964] bus_for_each_dev+0x78/0xe0 >> [ 1.450068] driver_attach+0x24/0x30 >> [ 1.450167] bus_add_driver+0x110/0x240 >> [ 1.450271] driver_register+0x60/0x128 >> [ 1.450376] __platform_driver_register+0x28/0x34 >> [ 1.450500] ams_driver_init+0x1c/0x28 >> [ 1.450609] do_one_initcall+0x78/0x2c8 >> [ 1.450714] kernel_init_freeable+0x2f8/0x59c >> [ 1.450831] kernel_init+0x30/0x150 >> [ 1.450932] ret_from_fork+0x10/0x20 >> [ 1.451073] ================================================================================ >> >> When applying the following patch: >> > That channel definition looks suspicious. Anyone shed light on what the channel scan index layout > is supposed to be? > There seem to be substantial gaps in used numbers. > If I read it right the offset to jump over the AUX_CHAN is too large (22 - should be 16) but > that still ends up with us going above the range of supported scan indexes. > > The PL Sequence mask used is GENMASK_ULL(59, 22) > > Whilst the bits are set, nothing actually reads them that I can see. > So why are they set and how are those channels supposed to work? > > So agreed buggy; no idea what it supposed to do! OK, so there are three groups of channels in this device, as set up by ams_init_module: - CTRL channels (xlnx,zynqmp-ams) - PS channels (xlnx,zynqmp-ams-ps) - PL channels (xlnx,zynqmp-ams-pl) According to the comment in ams_enable_channel_sequence, /* * Enable channel sequence. First 22 bits of scan_mask represent * PS channels, and next remaining bits represent PL channels. */ and indeed, the following code only touches the PS and PL registers. So I think we just need to add a check for chan->scan_index >= AMS_CTRL_SEQ_BASE, like in ams_read_raw. --Sean >> diff --git a/drivers/iio/adc/xilinx-ams.c b/drivers/iio/adc/xilinx-ams.c >> index f0b71a1220e0..1ced8cff461a 100644 >> --- a/drivers/iio/adc/xilinx-ams.c >> +++ b/drivers/iio/adc/xilinx-ams.c >> @@ -414,8 +414,17 @@ static void ams_enable_channel_sequence(struct iio_dev *indio_dev) >> >> /* Run calibration of PS & PL as part of the sequence */ >> scan_mask = BIT(0) | BIT(AMS_PS_SEQ_MAX); >> - for (i = 0; i < indio_dev->num_channels; i++) >> + for (i = 0; i < indio_dev->num_channels; i++) { >> + if (indio_dev->channels[i].scan_index >= 64) { >> + const struct iio_chan_spec *chan = &indio_dev->channels[i]; >> + >> + dev_warn(&indio_dev->dev, >> + "channel %d (%d %d.%d @ %lx) has scan_index %d\n", >> + i, chan->type, chan->channel, chan->channel2, >> + chan->address, chan->scan_index); >> + } >> scan_mask |= BIT_ULL(indio_dev->channels[i].scan_index); >> + } >> >> if (ams->ps_base) { >> /* put sysmon in a soft reset to change the sequence */ >> >> I see these additional outputs: >> >> [ 1.447457] iio iio:device0: channel 0 (0 0.0 @ 60) has scan_index 66 >> [ 1.451280] iio iio:device0: channel 1 (0 1.0 @ 6c) has scan_index 67 >> [ 1.451446] iio iio:device0: channel 2 (0 2.0 @ 78) has scan_index 68 >> [ 1.451612] iio iio:device0: channel 3 (0 3.0 @ 7c) has scan_index 69 >> [ 1.451777] iio iio:device0: channel 4 (0 4.0 @ 80) has scan_index 70 >> [ 1.451942] iio iio:device0: channel 5 (0 5.0 @ 84) has scan_index 71 >> [ 1.452107] iio iio:device0: channel 6 (0 6.0 @ 9c) has scan_index 72 >> >> Indicating that the issue is with the ams_ctrl_channels using the >> AMS_CTRL_CHAN_VOLTAGE macro. >> >> --Sean >> >